The present invention relates to a method for anticipating a change occurring in the condition of a patient's organism before the condition of a patient reaches a critical point, the condition of a patient's organism being monitored by the application of an appropriate measuring method and the determinations according to said measuring method being effected at appropriate time intervals.
In the monitoring of all types of phenomena it is usual that the variables subjected to monitoring be set with upper and lower limit values, the breaking of which produces a report. Such a report is also often referred to as an alarm. Momentary signal faults unrelated to the specific character of a quantity being monitored produce needless reports. Efforts have been made to eliminate needless and monitor-interfering reports by filtering the basic quantities in various ways and by delaying a report to be issued. The result of both filtering and delaying is a late appearance of a report received on a "legitimate" occurrence relative to the occurrence itself and even an alarm that is too late from the clinical point of view.
The reporting sensitivity can be regulated by the location of limit values in relation to the normal behaviour of a signal; a narrow limit value range produces more readily reports about deviations from the normal range while a wide limit value range may leave substantial changes unnoticed. The reporting philosophy based solely on a limit value range does not take the rate of changes into consideration. Even in the best of circumstances, the reporting system based en a limit value produces plenty of false alarms, the occurrence of which causes a temptation to either widen the limit value range or to switch off the alarm system.
If the normal value of a variable being monitored fluctuates between situations and individual, the fixed limit values must have a sufficiently wide range to include the entire natural fluctuation range for a quantity being monitored. Efforts have been made to enhance the reporting sensitivity by using automatic limit values, which are relatively narrow and which are set on either side of a standardized variable an a "suitable" distance according to sensible arguments. In the systems, the basic distances or ranges for automatic reports cannot be generally changed by the operator since the automatically set limit values indicate more sensitively the deviations of a quantity from a normal value, the use thereof often causes "needless" reports and is a temptation towards the adoption of fixed, wider limit values.
The behaviour of one variable can be anticipated if the pharmaco-kinetic and pharmaco-dynamic properties of pharmaceuticals having an effect thereon are known and mathematical patterns are used for calculating the dosage based effects on quantities being measured (Jan J. van der Aa JJ, Betoken JEW, van Oostrom JH, Gravenstein JS: Integration concepts for anesthesia workstation displays, J Clin Monit 1992; 8:51-2). This so-called projection technique is not based on observations but, instead, on expert systems which, on the other hand, are based on generalized allegations and experimentally discovered mathematical quantities.